Distributed Wireless Gateway

ABSTRACT

A distributed wireless gateway comprises several switches. Each switch is coupled to a respective set of wireless access points. When a given switch receives a packet from one of its wireless access points, it creates a mapping between that access point and the host that sent the packet to the access point. The given switch advertises to other switches in the distributed wireless gateway reachability information that maps that host to the switch, enabling the other switches to identify the given switch as the next hop when they receive a packet destined for that host.

BACKGROUND

A wireless network deployment typically comprises a deployment of accesspoints (APs) and their associated hosts. The wireless network caninclude a wireless local area network (LAN) controller (WLC) to whichthe APs are connected. The WLC provides a centralized monitoring andmanagement services to support the APs in the network. The WLCfacilitates centralized management, configuration, and support of thewireless network, and gives the network manager the ability to see allthe data and information related to the network.

A typical WLC is a standalone device. The WLC contains all wireless hostreachability information centrally located within its forwarding tables.The reachability information enables the WLC to provide switching amonghosts associated with the APs in the network. The WLC also acts as agateway between the wireless network and wired networks, such as a wiredLAN, the Internet, etc. The reachability information stored in the WLCinforms which APs to forward packets in order to reach the appropriatehost.

BRIEF DESCRIPTION OF THE DRAWINGS

With respect to the discussion to follow and in particular to thedrawings, it is stressed that the particulars shown represent examplesfor purposes of illustrative discussion, and are presented in the causeof providing a description of principles and conceptual aspects of thepresent disclosure. In this regard, no attempt is made to showimplementation details beyond what is needed for a fundamentalunderstanding of the present disclosure. The discussion to follow, inconjunction with the drawings, makes apparent to those of skill in theart how embodiments in accordance with the present disclosure may bepracticed. Similar or same reference numbers may be used to identify orotherwise refer to similar or same elements in the various drawings andsupporting descriptions. In the accompanying drawings:

FIG. 1A shows a network deployment in accordance with the presentdisclosure.

FIG. 1B shows a VxLAN-based network deployment in accordance with thepresent disclosure.

FIG. 1C shows a distributed gateway with a single network segment.

FIG. 2 shows details of a VxLAN packet.

FIG. 3 shows processing a control plane packet in accordance with thepresent disclosure.

FIG. 4 shows processing a data plane packet in accordance with thepresent disclosure.

FIG. 5 shows forwarding an ingress packet in accordance with the presentdisclosure.

FIGS. 6A and 6B show illustrative examples of traffic flows inaccordance with the present disclosure.

FIG. 7 illustrates an example of BUM traffic in accordance with thepresent disclosure.

FIG. 8 shows network device that can be adapted to operate in accordancewith the present disclosure.

DETAILED DESCRIPTION

The centralized nature of a conventional WLC means that all trafficbetween hosts connected to different APs flow through the WLC. Moresignificantly, all traffic between hosts within the wireless network andexternal wired networks (e.g., the Internet) flows through the WLC. Assuch, a conventional WLC can become a bottleneck for access to the wirednetwork under high traffic loads, thus degrading performance. Likewisefor traffic between hosts associated with different APs because suchtraffic flows through the WLC. Furthermore, because all traffic flowsthrough the WLC, the WLC represents a single point failure.

In accordance with some embodiments of the present disclosure, thegateway functionality of the WLC can be distributed among severalindependently operating network devices to distribute the traffic amongthe network devices. Further in accordance with the present disclosure,the network devices comprising the distributed gateway can be configuredto synchronize/share their host reachability information in order tomaintain reachability between hosts connected to different APs in thedistributed gateway configuration.

In the following description, for purposes of explanation, numerousexamples and specific details are set forth in order to provide athorough understanding of embodiments of the present disclosure.Particular embodiments as expressed in the claims may include some orall of the features in these examples, alone or in combination withother features described below, and may further include modificationsand equivalents of the features and concepts described herein.

Referring to FIG. 1A, network 100 represents an illustrative example ofa network deployment in accordance with some embodiments of the presentdisclosure. Network 100 provides a communication infrastructure thatallows hosts 12 to communicate with each other and with data network 14.Hosts 12 can be server systems (e.g., application servers, file servers,web sites, database systems, etc.) and client devices (e.g., laptopcomputers, desktop computers, mobile devices, and the like). Datanetwork 14 can include the Internet (e.g., via a public switchedtelephone network, PSTN), a local area network (LAN) or wide areanetwork (WAN) in an enterprise or campus, and so on. Data network 14 canbe referred to as the wired network.

Network 100 can comprise network devices 102, 104. In accordance withsome embodiments, network devices 102, 104 can be routers, switches,software running on generic servers, and so on. For reasons that willbecome clear further below, network devices 102 will be referred toherein as core tunnel endpoints (core TEs), and network devices 104 willbe referred to herein as edge tunnel endpoints (edge TEs). Generally,tunnel endpoints are network devices that are configured to supportpacket tunneling in accordance with a tunneling protocol. Tunnelendpoints at each end of a tunnel encapsulate packets for transmissionover the tunnel and decapsulate packets received from the tunnel. Theexample in FIG. 1A shows three core TEs and four edge TEs, although itwill be appreciated that the configuration shown is merely anillustrative example and that network 100 can be deployed with more orfewer core and edge TEs. Core TEs 102 can be connected to other core TEsand to edge TEs 104 by physical connections (e.g., electrical cables,fiber optic cables, etc.), wireless connections, or a combination ofphysical and wireless connections. Network 100 can be managed andotherwise maintained by a user (e.g., network administrator), forexample, using controller 16.

Core TEs 102 can connect to data network 14 via communication channels106. In some embodiments, for example, communication channels 106 can bephysical connections (e.g., electrical cables, fiber optic cables,etc.), wireless connections, or a combination of physical and wirelessconnections. Some of the communication channels can be wireless. EdgeTEs 104 can access data network 14 via the respective core TEs 102 towhich the edge TEs are connected.

Hosts 12 can access data network 14 via an edge TE or a core TE. Forexample, hosts H1-H8 wirelessly communicate with their respective edgeTEs to access data network 14. On the other hand, hosts H9-H10 aredirectly connected to their respective core TEs to access the datanetwork.

Core TEs 102 and edge TEs 104 can communicate with each other viavirtual tunnels (tunnels) 112. Tunneling is a known and well understoodcommunication technology. Briefly, when a source host wants to transmitan original packet to a destination host that is reachable over atunnel, the source host can transmit the original packet to an endpointof the tunnel (tunnel endpoint). The tunnel endpoint encapsulates theoriginal packet in accordance with a tunneling protocol to create atunneling packet (tunneled packet, encapsulated packet, etc.) thatcontains the original packet in its payload and designates a remotetunnel endpoint as its destination. The tunneling packet is routed tothe remote tunnel endpoint, which then decapsulates the tunneling packetto recover the original packet. The remote tunnel endpoint then forwardsthe recovered original packet to the next hop.

Traffic between core TEs 102 and edge TEs 104 can be tunneled using anysuitable tunneling protocol such as Virtual Extensible Local AreaNetwork (VxLAN), Generic Routing Encapsulation (GRE), Internet ProtocolSecurity (IPSec), and so on. Merely for discussion purposes, however,VxLAN tunneling will be referenced whenever the discussion calls forspecific examples of a tunneling protocol.

In accordance with the present disclosure, core TEs 102 can beconfigured with multiple tunnels. Core TEs 102 can be configured toperform tunnel endpoint bridging so that a given core TE that isconfigured with several tunnels can reach corresponding tunnel endpoints(core TEs and edge TEs 102, 104) at the other ends of those tunnels.Bridging generally refers to any forwarding at Layer 2 (L2, the datalink layer) of the Open Systems Interconnection (OSI) model based on apacket's L2 header. In the context of the present disclosure, tunnelendpoint bridging involves a tunnel endpoint receiving a tunneled packeton one of its tunnels, decapsulating the packet, re-encapsulating thepacket, and forwarding the re-encapsulated packet on another of itstunnels.

Referring to FIG. 1B, network 150 represents a specific example of anetwork in accordance with the present disclosure to illustrate aspectsof the present disclosure. Network 150 is a VxLAN deployment based onthe VxLAN protocol to provide tunneling among its constituent core TEs102 and edge TEs 104. Devices that are tunnel endpoints of a tunnel in aVxLAN are referred to as VxLAN tunnel endpoints (VTEPs). Core TEs 102can be configured as VTEPs. Edge TEs 104 can be configured as wirelessaccess points (APs) to provide their respective associated hosts H1-H8with wireless access to data network 14 via the core TEs. The edge TEsare also configured as VTEPs to communicate with their respective coreTEs. Because VxLAN tunneling is the reference for specific examples, theremainder of the present disclosure will refer to core TEs 102 as“aggregation VTEPs,” or more simply as “VTEPs.” Edge TEs 104 will bereferred to simply as APs with the understanding that APs are alsoconfigured as VTEPs; APs are connected to their respective aggregationVTEPs and communicate over VxLAN tunnels 160. The aggregation VTEPsconstitute a VxLAN control plane for the purpose of exchanging VxLANreachability information.

A VTEP that is connected to one or more APs in a network segment can bereferred to as an “aggregation” VTEP because the VTEP aggregates trafficfrom hosts associated with that network segment. VTEP 3, on the otherhand, can be referred to as a regular (non-aggregation) VTEP.

The APs may constitute or otherwise define one or more wireless networksegments 156 in network 150. Typically, and as used herein, the term“segment” refers to an L2 segment where devices in the segmentcommunicate at the data link layer by transmitting data in units calledframes (e.g., Ethernet frames). For example, AP1 defines a networksegment identified by the Service Set Identifier (SSID) SSID-A and AP4defines another network segment identified as SSID-C. A network segmentcan span APs that are connected to different VTEPs; AP2 and AP3, forexample, define such a network segment identified as SSID-B.

When a network segment spans multiple aggregation VTEPs, those VTEPstogether can be referred to as a “distributed gateway” for hostsassociated with that network segment. Consider the network segmentSSID-B, for example. SSID-B spans VTEP 1 and VTEP 2 because it includesAP2, which is connected to VTEP 1, and AP3, which is connected to VTEP2. Accordingly, VTEP 1 and VTEP 2 can function as a distributed gatewayfor hosts associated with SSID-B. Referring for a moment to FIG. 1C,network 170 shows a larger collection of VTEPs configured as distributedgateway 172 in accordance with the present disclosure. The example showsa network segment that includes AP1 to AP6. The respective VTEPs towhich the APs are connected, namely VTEP 1, VTEP 2, VTEP 3, collectivelyconstitute distributed gateway 172. The collection of VTEPs functionallyrepresents a gateway to data network 14 for devices (hosts, APs)connected to the VTEPs. The gateway is “distributed” in that each VTEPcan provide access to data network 14, independently of the other VTEPs.The gateway functionality is distributed among the VTEPs rather thanbeing centralized in a single device. The configuration shown in FIG. 1Crepresent an example of a WLC whose gateway functionality is provided bygateway 172 and whose AP control and management functions are providedby WLC management module 18.

Returning to FIG. 1B, each network segment 156 represents a subset ofthe network, and includes all devices that can reach one another atLayer 2 (L2) of the OSI (Open Systems Interconnection) model (i.e.,devices that can reach one another via bridging). Accordingly, eachnetwork segment 156 can be referred to as a broadcast (communication)domain or an L2 domain. Generally, a broadcast domain refers to a groupof devices that can reach each other at Layer 2 of the OSI model thatbelong to the same network segment.

Referring to FIG. 2, an anatomy of VxLAN tunneling packet 200 inaccordance with the VxLAN protocol is shown. The VxLAN protocol is awell understood and standardized protocol. For purposes of the presentdisclosure, only certain fields of VxLAN packet 200 are highlighted.Beginning from the interior of VxLAN packet 200, data field 202 is thepayload (inner packet) of the VxLAN packet. Data field 202 is an L2frame (e.g., an Ethernet frame) that represents the network data fromthe sending VTEP. Data field 202 contains payload 222, which is theactual data packet of interest (e.g., data from one host to anotherhost). Payload 222 will include Inner Source and Destination Internetprotocol (IP) addresses 222 a, 222 b, which are the respective IPaddresses of the source host and the destination host. Data field 202also includes Inner Source media access control (MAC) address 226 andInner Destination MAC address 224. The Inner Source MAC address is theMAC address of the sending host, and the Inner Destination MAC addressis the MAC address of the destination host.

Data field 204 is an Outer IP Header of VxLAN packet 200 that includesOuter Source IP address 242, which is the IP address of the source VTEPthat sends the tunneled packet, and Outer Destination IP address 244,which is the IP address of the destination VTEP that receives the VxLANpacket.

Data field 206 is an Outer Ethernet Header of the VxLAN packet thatincludes Outer Source MAC address 262 and Outer Destination MAC address264. The Outer Source MAC address is the MAC address of the VTEP (e.g.,an edge TE or another core TE) connected to the core TE. The OuterDestination MAC address is the MAC address of the destination VTEP(e.g., the destination core TE).

Data field 208 is a VxLAN header that, together with the original L2frame (inner packet), goes in the UDP payload. The VxLAN header includesVxLAN network identifier (VNI) 282 which is a 24-bit quantity thatidentifies an L2 domain. An aggregation VTEP can support communicationover multiple L2 domains. Aggregation VTEP 2 in FIG. 1B, for example,supports communication for L2 domain SSID-B and another separate L2domain SSID-C. The VxLAN header identifies which L2 domain is associatedwith a given VxLAN packet.

To illustrate an example of processing a VxLAN packet in accordance withthe present disclosure, consider host H5 and AP3 in FIG. 1B. Supposehost H5 wants to send a packet (original packet) to another host (e.g.,host H3) on the network. The process begins with Host H5 transmittingthe original packet to AP3. AP3 will transmit a VxLAN packet thatencapsulates the original packet to aggregation VTEP 2. The VxLAN packetfrom AP3 to VTEP 2 will include the following information:

-   -   Outer Source MAC address, 264—MAC address of AP3 (source of the        VxLAN packet)    -   Outer Destination MAC address, 262—MAC address of aggregation        VTEP 2 (next hop in the underlay, and in this case a tunnel        endpoint of the VxLAN packet)    -   Outer Source IP address, 242—IP address of AP3    -   Outer Destination IP address, 244—IP address of aggregation VTEP        2    -   Inner Source MAC address, 226—MAC address of host H5 (source of        the original packet)    -   Inner Destination MAC address, 224—MAC address of host H3        (destination of the original packet)    -   payload, 222—contains the original packet, which includes:        -   Inner Source IP address, 282—IP address of host H5 (source            of the original packet)        -   Inner Destination IP address, 284—IP address of host H3            (destination of the original packet)

To illustrate a VTEP to VTEP bridging example, we will continue theabove example with a description of how VTEP 2 processes the VxLANpacket from AP3. The process begins with VTEP 2 receiving theabove-described VxLAN packet from AP3 over one tunnel. VTEP 2 performsthe bridging operation by decapsulating the received VxLAN packet torecover the original packet and re-encapsulating the recovered originalpacket in a subsequent VxLAN packet that is then sent to VTEP 1 overanother tunnel. The VxLAN packet from VTEP 2 to VTEP 1 will include thefollowing information:

-   -   Outer Source MAC address, 264—MAC address of VTEP 2 (source of        the VxLAN packet)    -   Outer Destination MAC address, 262—MAC address of VTEP 1 (next        hop in the underlay, and in this case a tunnel endpoint of the        VxLAN packet)    -   Outer Source IP address, 242—IP address of VTEP 2    -   Outer Destination IP address, 244—IP address of VTEP 1    -   Inner Source MAC address, 226—MAC address of host H5 (source of        the original packet).    -   Inner Destination MAC address, 224—MAC address of host H3        (destination of the original packet) payload, 222—contains the        original packet, which includes:        -   Inner Source IP address, 282—IP address of host H5 (source            of the original packet)        -   Inner Destination IP address, 284—IP address of host H3            (destination of the original packet)

For the remaining discussion, and without loss of generality, referencewill be made to the configuration shown in FIG. 1B in order to provide aspecific example of core TEs 102 and edge TEs 104, namely aggregationVTEPs (or more simply VTEPs) and AP VTEPs (or more simply APs)respectively. It will be appreciated that the following description,although made in the context of VxLAN and VTEP technology, may beadaptable to other tunneling protocols and tunnel endpoints.

Referring to FIG. 3, the discussion will now turn to a high leveldescription of processing in a core TE to process control plane packetsin support of the functionality of a distributed gateway in accordancewith the present disclosure. The description will refer to anaggregation VTEP (e.g., FIG. 1B) merely as an illustrative example. Insome embodiments, for instance, the aggregation VTEP can includecomputer executable program code, which when executed by a processor(e.g., 808, FIG. 8), can cause the processor to perform operations inaccordance with FIG. 3.

At operation 302, the aggregation VTEP can receive an ingress packet onone of its ports. The ingress packet can be encapsulated (e.g., a VxLANpacket) or not encapsulated.

At decision point 304, if the received ingress packet is destined forthe aggregation VTEP, then processing in the aggregation VTEP canproceed to decision point 306. If the destination of the receivedingress packet is not the aggregation VTEP, then processing in theaggregation VTEP can proceed to operation 304 a to forward the ingresspacket, details of which are described in connection with FIG. 5. Insome embodiments, the destination IP address can be used to determine ifthe ingress packet is destined for the aggregation VTEP, for example, bycomparing the destination IP in the ingress packet to the IP address ofthe aggregation VTEP. In the case of a tunneled (e.g., VxLAN) packet,the determination can be based on the inner destination IP address (222b, FIG. 2).

At decision point 306, if the received ingress packet is notencapsulated in a tunnel packet, then processing in the aggregation VTEPcan proceed to decision point 308. If the received ingress packet isencapsulated (e.g., a VxLAN packet), then processing in the aggregationVTEP can proceed to operation 306 a, where the aggregation VTEP candecapsulate the ingress packet to recover the inner packet, beforeproceeding to decision point 308; for discussion purposes, the recoveredinner packet will continue to be referred to as the “ingress packet.”

At decision point 308, if the ingress packet is a control plane packetthen processing in the aggregation VTEP can proceed to decision point310. If the ingress packet is not a control plane packet then theingress packet can be deemed to be a data plane packet; processing inthe aggregation VTEP can proceed to operation 308 a to process a dataplane packet, details of which are described in connection with FIG. 4.In some embodiments, for instance, the aggregation VTEPs can useEthernet virtual private network (EVPN), a known technology for Layer 2internetworking. EVPN defines network layer reachability information(NLRI) by extending the Border Gateway Protocol (BGP). In the context ofBGP, the presence of a BGP header in the ingress packet can mean thatthe ingress packet is a control plane packet.

At decision point 310, if the ingress packet designates a next hop, thenprocessing in the aggregation VTEP can proceed to operation 312. If theingress packet does not designate a next hop, then processing in theaggregation VTEP can proceed to decision point 314. Using BGP as anexample, the Address Family Identifier (AFI) and Subsequent AddressFamily Identifier (SAFI) data fields in the ingress (control plane)packet can be used to determine if we have an EVPN route. If the routetype in the BGP EVPN NLRI is Type 2 (reference operation 412, FIG. 4),then we have a MAC-IP route and the ingress packet includes MACreachability information (i.e., designates a next hop) that specifiesthe MAC address of a given host. Reference operation 416 in FIG. 4

At operation 312, the aggregation VTEP can learn the next hop that iscontained in the ingress packet. In some embodiments, for example, theaggregation VTEP can include a forwarding database (FDB) that containsinformation to facilitate the forwarding of packets through the VTEP.FDBs are known data structures in a network device and are used toidentify a next hop for a given packet. Using the MAC reachabilityinformation contained in the ingress packet, the aggregation VTEP canstore an entry, in its FDB, that provides a mapping between the MACaddress of the given host and the IP address of the sender (e.g., aVTEP) of the ingress packet. The mapping informs the aggregation VTEPthat the IP address is the next hop for a packet destined for the givenhost. This aspect of the present disclosure is referenced below inconnection with FIG. 5. Processing of the ingress packet can be deemedcomplete.

At decision point 314, if the ingress packet designates a flood list,then processing in the aggregation VTEP can proceed to operation 316. Ifthe received ingress packet does not designate a flood list, thenprocessing of the received ingress packet can be deemed complete. Floodlists are known. Certain packets, referred to as broadcast, unicastunknown, or multicast (BUM) packets, are broadcast to multipledestinations rather than to a single destination. The flood list informsthe network device (e.g., the aggregation VTEP) the list of devices towhich such packets are broadcast for a particular broadcast domain.Referring to the BGP example, for instance, if the route type in the BGPEVPN NLRI is Type 3 (reference operation 422, FIG. 4), then we have anInclusive Multicast Ethernet Tag (IMET) route and the ingress packetcontains flood list information; processing can proceed to operation316.

At operation 316, when the ingress packet designates a flood list, theaggregation VTEP can update its flood list for that broadcast domain toinclude the VTEP that sent the ingress packet (sending VTEP). In someembodiments, for example, the IP address of the sending VTEP can beobtained from the received BGP EVPN IMET route. The IP address of thesending VTEP can be added to the aggregation VTEP's flood list for thatbroadcast domain so that BUM traffic is broadcast to the sending VTEPalong with other neighbors in the flood list. This aspect of the presentdisclosure is referenced below in connection with FIG. 5. Processing ofan ingress packet received from an aggregation VTEP can be deemedcomplete.

Referring to FIG. 4, the discussion will now turn to a high leveldescription of processing in a core TE to process data plane packets insupport of the functionality of a distributed gateway in accordance withthe present disclosure. The description will refer to an aggregationVTEP as a specific example. In some embodiments, for instance, theaggregation VTEP can include computer executable program code, whichwhen executed by a processor (e.g., 808, FIG. 8), can cause theprocessor to perform operations in accordance with FIG. 4. Theoperations shown in FIG. 4 continue from operation 308 a in FIG. 3.

At decision point 402, if the ingress packet comes from an AP, thenprocessing in the aggregation VTEP can proceed according to operation412. If the ingress packet does not come from an AP, then theaggregation VTEP can proceed operation 404 to forward the ingresspacket, details of which are described in connection with FIG. 5. Insome embodiments, for example, the outer source IP address (e.g., 242,FIG. 2) contained in the encapsulated form of ingress packet can be usedto determine whether the ingress packet comes from an AP or a non-APdevice.

At operation 412, the aggregation VTEP can identify the host behind theAP that sent the ingress packet. In some embodiments, for example, theAP can be identified by its outer source MAC address (e.g., 264, FIG. 2)or its outer source IP address (e.g., 244) contained in the encapsulatedform of the ingress packet. Similarly, the host can be identified by itsinner source MAC address (e.g., 226) or its inner source IP address(e.g., 222 a) contained in the encapsulated ingress packet.

At operation 414, the aggregation VTEP can store or otherwise learn amapping between the identified AP and the identified host. Theaggregation VTEP can install an entry in the FDB that maps between theidentified AP and the identified host. In some embodiments, for example,the MAC address of the identified AP and the MAC address of theidentified host can be installed in the FDB. As will be explained inconnection with FIG. 5, this mapping allows the aggregation VTEP toselect the identified AP as the next hop for the identified host.

At operation 416, the aggregation VTEP can advertise itself to the otheraggregation VTEPs to inform the other aggregation VTEPs that it is thenext hop for the identified host. Accordingly, the aggregation VTEP canadvertise a BGP EVPN MAC-IP route (Type 2 route) to the otheraggregation VTEPs to inform the other aggregation VTEPs that it is thenext hop for the identified host. See decision point 310 in FIG. 3 forthe processing of the BGP EVPN MAC-IP route.

At operation 418, the aggregation VTEP can store the AP in its floodlist for the broadcast domain that includes the AP. The flood listinforms the network device (e.g., the aggregation VTEP) the list ofdevices to which BUM packets are broadcast As explained above, abroadcast domain (also referred to as an L2 domain) is a subset of anetwork that includes all devices that can reach one another at Layer 2of the OSI model. In some embodiments, the aggregation VTEP can maintaina flood list for each broadcast domain with which it is currentlyconfigured. Referring to FIG. 1B, for instance, aggregation VTEP 2 showsat least three broadcast domains: the broadcast domain identified bySSID-B, the domain identified by SSID-C, and so on. A given flood listcontains a list of the devices in the corresponding broadcast domainlearned by the aggregation VTEP. In some embodiments, the aggregationVTEP can use the VNI (e.g., 282, FIG. 2) contained in the receivedingress packet to identify the corresponding local VLAN on the VTEP. Theidentified local VLAN represents the broadcast domain. The AP (e.g., itsMAC address) can be added to the flood list of the aggregation VTEP thatis associated with the identified broadcast domain.

At decision point 420, if the aggregation VTEP is seeing traffic on thebroadcast (L2) domain identified at operation 418 for the first time,then processing in the aggregation VTEP can proceed to operation 422. Ifthe aggregation VTEP has previously seen traffic on the broadcast (L2)domain identified at operation 418, then processing in the aggregationVTEP can proceed to operation 424 to forward the ingress packet inaccordance with the operations shown in FIG. 5. In some embodiments, forexample, the flood list associated with each broadcast domain defined inthe aggregation VTEP can include an associated flag that is set or notset to indicate whether traffic on that broadcast domain has beenpreviously detected.

At operation 422, the aggregation VTEP can advertise itself to the otherVTEPs in the VxLAN control plane (FIG. 1B) to inform those devices thatit is a flood neighbor of the broadcast domain that includes the APidentified at operation 312. In some embodiments, for example, theaggregation VTEP can advertise a BGP EVPN IMET route (Type 3 route) tothe other devices to indicate its participation in the flood list forthe identified broadcast domain. See decision point 314 in FIG. 3 forthe processing of the BGP EVPN IMET route.

At operation 424, the aggregation VTEP can forward the ingress packet,details of which are described in FIG. 5.

Referring to FIG. 5, the discussion will now turn to a high leveldescription of processing in a core TE to support forwarding of dataplane packets in a distributed gateway in accordance with the presentdisclosure. The description will refer to an aggregation VTEP as aspecific example. In some embodiments, for instance, the aggregationVTEP can include computer executable program code, which when executedby a processor (e.g., 808, FIG. 8), can cause the processor to performoperations in accordance with FIG. 5. The operations in FIG. 5 continuefrom operation 304 a in FIG. 3 and operations 404, 424 in FIG. 4.

At decision point 502, if the received ingress packet is a broadcastpacket or a multicast packet, then processing in the aggregation VTEPcan proceed to operation 508 to handle broadcast and multicast packetsin accordance with the present disclosure. If the received ingresspacket is neither a broadcast packet nor a multicast packet, thenprocessing in the aggregation VTEP can proceed to operation 504. In someembodiments, this determination can be made based on the inner packet ofthe received ingress packet.

-   -   Broadcast Packet—In some embodiments, the aggregation VTEP can        determine that the recovered inner packet is a broadcast packet        based on its destination MAC address. Referring to the VxLAN        packet shown in FIG. 2, for example, a broadcast packet can be        detected based on the inner destination MAC address (224)        contained in the inner packet. A broadcast packet is intended to        target all nodes on the network, and can be identified by a        destination MAC address that contains all 1's, namely:        -   FF:FF:FF:FF:FF:FF.    -   Multicast Packet—Similarly, in some embodiments, the aggregation        VTEP can determine that the recovered inner packet is a        multicast packet based on its inner destination MAC address        (224). A multicast packet can be identified when the least        significant bit in the first octet of the MAC address is set to        ‘1’; for example:        -   bbbbbbb1:xx:xx:xx:xx:xx,    -   where, b is ‘0’ or ‘1’ and x is 0-F.

At operation 504 the aggregation VTEP can determine a next hopdestination to which the inner packet can be forwarded. In someembodiments, for example, the aggregation VTEP can determine the nexthop from its FDB using the inner destination MAC address contained inthe inner packet. The FDB may include destination MAC address-to-nexthop mappings that were learned (312, FIG. 3) from previously advertisedBGP EVPN MAC-IP routes (416, FIG. 4).

At decision point 506, if the aggregation VTEP's FDB does not map thedestination MAC address of the inner packet to a next hop, the innerpacket can be deemed to be an “unknown unicast” packet and processing inthe aggregation VTEP can proceed to operation 508 to process an unknownunicast packet in accordance with the present disclosure. If the FDBmaps the destination MAC to a next hop, then processing in theaggregation VTEP can proceed to operation 510.

At operation 508, the aggregation VTEP can process a Broadcast, UnknownUnicast, and Multicast (BUM) packet in accordance with the presentdisclosure. The aggregation VTEP can identify and access an appropriateflood list to identify flood neighbors. In the case of a VxLAN packet,for example, the flood list can be identified based on the VNI in theVxLAN header in the BUM packet. The VNI can be used to do a lookup onthe local VNI-to-VLAN mapping in the aggregation VTEP to identify the IDof the VLAN. In the case of a non-VxLAN packet, we look for a VLAN(802.1Q) header in the packet or at the VLAN associated with the ingressinterface to obtain the VLAN ID. In all cases, the VLAN ID isrepresentative of the broadcast domain on which to flood the packet.Neighbors in the flood list can include front panel ports of theaggregation VTEP and other VTEPs in the network, including aggregationVTEPs identified in previously advertised BGP EVPN IMET routes (422,FIG. 4). The aggregation VTEP can forward one copy of the inner packetto each neighbor specified in the identified flood list. Processing ofthe received ingress packet by the aggregation VTEP can be deemedcomplete.

At operation 510, the aggregation VTEP can forward the inner packet tothe next hop. If the next hop is a VTEP, then the aggregation VTEP canencapsulate the inner packet to produce an egress VxLAN packet that canthen be forwarded on the tunnel associated with the destination VTEP.Processing of the received ingress packet by the aggregation VTEP can bedeemed complete.

The discussion will now turn to illustrative traffic flow examples toprovide context for the operations shown in FIGS. 3, 4, and 5. Theexamples will be illustrated using a VxLAN configured network.

Referring to FIG. 6A, network 600 includes distributed gateway 602comprising aggregation VTEPs A, B, and C, and access point VTEPs AP1 toAP6 connected to their respective aggregation VTEPs. The APs providewireless access for their respective associated hosts H1 to H6. Fordiscussion purposes, AP1 and AP3 are in the same network segment. Weconsider a packet sent from host H1 to host H3. FIG. 6A shows trafficflow when processing a packet sent from host H1 to host H3 in accordancewith operations shown in FIGS. 3 and 4. The processing is described interms of a series of actions identified by time indices that arerepresented in the figure as circled numerals. The time indices providea general order of the sequencing of actions. It is understood that theactual order in which the actions are performed will depend onparticular embodiments of the present disclosure. References tooperations in FIGS. 3 and 4 are made when appropriate. References toaggregation VTEPs A, B, and C are shortened to VTEPs A, B, and C.

At time index 1, host H1 transmits a (original) packet to AP1 with thefollowing address information:

-   -   SRC-M: H1-MAC    -   DST-M: H3-MAC    -   SRC: H1-IP    -   DST: H3-IP    -   [H1 PAYLOAD]

At time index 2, AP1 encapsulates the original packet in a VxLAN packetand forwards the VxLAN packet to VTEP A with the following IP addressinformation:

-   -   OUTER SRC: AP1-IP    -   OUTER DST: AGG_A-IP        -   INNER SRC-M: H1-MAC        -   INNER DST-M: H3-MAC        -   INNER SRC: H1-IP        -   INNER DST: H3-IP        -   [H1 PAYLOAD]            Aggregation VTEP A receives the VxLAN packet from AP1            (operation 302) and decapsulates the received VxLAN packet            to recover the inner original packet (operation 306 a). It            can be appreciated that processing will proceed to FIG. 4            via operation 308 a.

At time index 3, VTEP A identifies the host behind AP1 (operation 412),which is host H1, and learns the mapping between host H1 and AP1(operation 414). The mapping maps the MAC address of host H1 and the IPaddress of AP1, and is installed in the FDB of VTEP A.

At time index 4, VTEP A advertises an EVPN Type 2 (MAC-IP) route to theother aggregation VTEPs in network 600 (operation 416). The Type 2 routeserves to inform the other aggregation VTEPs that VTEP A is the next hopfor packets destined to host H1.

At time index 5, the other aggregation VTEPs comprising distributedgateway 602 receive and process the Type 2 route in accordance with thepresent disclosure. Consider VTEP B, for example, where the VTEP learnsthe host H1 to VTEP A mapping in its FDB (operation 312). Although notshown, VTEP C also installs the host H1 to VTEP A mapping in its FDB.

At time index 6, VTEP A adds AP1 to a flood list stored in VTEP A thatis associated with the broadcast domain that includes AP1 (operation418). The flood list will inform VTEP A to include AP1 as a floodneighbor when broadcasting BUM packets to that broadcast domain.

At time index 7, VTEP A advertises an EVPN Type 3 (IMET) route to theother aggregation VTEPs in network 600, if this is the first time seeingtraffic in the broadcast domain of AP1 (operation 422). The Type 3 routeserves to inform the other aggregation VTEPs to include VTEP A in theirrespective flood lists.

At time index 8, each aggregation VTEP processes the Type 3 route inaccordance with the present disclosure. Consider VTEP B, for example,where VTEP B adds VTEP A to its flood list (operation 316) for thatbroadcast domain. Although not shown, VTEP C also adds VTEP A to itsflood list for that broadcast domain.

FIG. 6B continues the example of FIG. 6A and shows traffic flow whenprocessing a packet sent from host H4 to host H1. FIG. 6B shows trafficflow when processing a packet sent from host H4 to host H1 in accordancewith operations shown in FIG. 5, for the case where the packet is not aBUM packet; FIG. 6C describes processing for a BUM packet. It will beunderstood that VTEP B will perform processing per FIGS. 3 and 4 asdescribed above in FIG. 6A, but those operations are omitted in order tofocus on operations in FIG. 5. The discussion continues from the pointof view of VTEP B beginning at a time subsequent to time index 8. It isunderstood that the actual order in which the actions are performed willdepend on particular embodiments of the present disclosure. Referencesto operations in FIG. 5 are made when appropriate. References toaggregation VTEPs A, B, and C are shortened to VTEPs A, B, and C.

At time index 9, host H4 transmits a (original) packet to AP4 with thefollowing address information:

-   -   SRC-M: H4-MAC    -   DST-M: H1-MAC    -   SRC: H4-IP    -   DST: H1-IP    -   [H4 PAYLOAD]

At time index 10, AP4 encapsulates the original packet in a VxLAN packetand forwards the VxLAN packet to VTEP B with the following IP addressinformation:

-   -   OUTER SRC: AP4-IP    -   OUTER DST: AGG_B-IP        -   INNER SRC-M: H4-MAC        -   INNER DST-M: H1-MAC        -   INNER SRC: H4-IP        -   INNER DST: H1-IP        -   [H4 PAYLOAD]

At time index 11, VTEP B receives the VxLAN packet from AP4 anddecapsulates the received VxLAN packet to recover the inner originalpacket and will proceed to FIG. 5 via operation 424. Because thedestination MAC address in the recovered inner packet is neither abroadcast address nor a multicast address (N branch of decision point502), VTEP B performs a lookup in its FDB to identify a next hop for therecovered inner packet (operation 504).

At time index 12, because VTEP B learned of the host H1-to-VTEP Amapping at time index 5 in FIG. 6A, VTEP B finds that the next hop forthe recovered inner packet is VTEP A; the recovered inner packet is aknown unicast packet (N branch of decision point 506). Accordingly, VTEPB encapsulates the inner packet in a VxLAN egress packet and forwardsthe egress packet to VTEP A (operation 510). Processing of the recoveredinner packet by VTEP B can be deemed complete.

At time index 13, VTEP A decapsulates the VxLAN packet received fromVTEP B to recover the inner packet and will proceed to FIG. 5 viaoperation 404. Because the destination MAC address in the recoveredinner packet is neither a broadcast address nor a multicast address,VTEP A performs a lookup in its FDB to identify a next hop for therecovered inner packet (operation 504).

At time index 14, because VTEP A learned of the H1-to-AP1 mapping attime index 3 in FIG. 6A, VTEP A finds that the next hop is AP1.Accordingly, VTEP A encapsulates the inner packet in a VxLAN egresspacket and forwards the egress packet to AP1 (operation 510). Processingof the recovered inner packet by VTEP A can be deemed complete.

At time index 15, AP1 decapsulates the VxLAN packet received from VTEP Ato recover the inner packet. AP1 forwards the inner packet to host H1,for example, based on the destination MAC address contained in the innerpacket.

Referring to FIG. 7 the discussion will turn to a description ofprocessing BUM traffic in accordance with the flow shown in FIG. 5. FIG.7 uses the configuration of FIG. 6A to illustrate traffic flow for thecase where the packet from host H1 is a BUM packet.

At time index 1, host H1 transmits a packet to AP1 with the followingaddress information:

-   -   SRC-M: H1-MAC    -   DST-M: xxMACxx    -   SRC: H1-IP    -   DST: ???    -   [H1 PAYLOAD]        where xxMACxx is a broadcast MAC address (FF:FF:FF:FF:FF:FF) or        a multicast MAC address (bbbbbbb1:xx:xx:xx:xx:xx), or where the        destination IP address is unknown.

At time index 2, AP1 encapsulates the original packet in a VxLAN packetand forwards the VxLAN packet to VTEP A with the following IP addressinformation:

-   -   OUTER SRC: AP1-IP    -   OUTER DST: AGG_A-IP        -   INNER SRC-M: H1-MAC        -   INNER DST-M: xxMACxx        -   INNER SRC: H1-IP        -   INNER DST: ???        -   [H1 PAYLOAD]

Aggregation VTEP A receives the VxLAN packet from AP1 (operation 302)and decapsulates the received VxLAN packet to recover the inner originalpacket (operation 306 b). The packet is processed in accordance withFIGS. 3 and 4 as described above in connection with FIG. 6A, whereprocessing leads to FIG. 5.

At time index 3, VTEP A will detect a BUM packet, either at decisionpoint 502 or decision point 506, and process the BUM packet at operation508. More specifically, VTEP A will use the flood list associated withthe L2 domain associated with the VNI in the VxLAN header, flood thepacket to each neighbor in that flood list.

Referring now to FIG. 8, we show an example of a network device inaccordance with some embodiments of the present disclosure. In someembodiments, network device 800 can be a switch (e.g., core TE, FIG. 1A,VTEP A, FIG. 1B). As shown, network device 800 includes a managementmodule 802, an internal fabric module 804, and a number of I/O modules806 a-806 p. Management module 802 includes the control plane (alsoreferred to as control layer) of network device 800 and can include oneor more management CPUs 808 for managing and controlling operation ofnetwork device 800 in accordance with the present disclosure. Eachmanagement CPU 808 can be a general purpose processor, such as anIntel®/AMD® x86 or ARM® processor, that operates under the control ofsoftware stored in a memory (not shown), such as dynamic random accessmemory (DRAM). Control plane refers to all the functions and processesthat determine which path to use, such as routing protocols, spanningtree, and the like.

Internal fabric module 804 and I/O modules 806 a-806 p collectivelyrepresent the data plane of network device 800 (also referred to as datalayer, forwarding plane, etc.). Internal fabric module 804 is configuredto interconnect the various other modules of network device 800. EachI/O module 806 a-806 p includes one or more input/output ports 810 a-810p that are used by network device 800 to send and receive networkpackets. Each I/O module 806 a-806 p can also include a packet processor812 a-812 p. Each packet processor 812 a-812 p can comprise a forwardinghardware component (e.g., application specific integrated circuit(ASIC), field programmable array (FPGA), digital processing unit,graphics coprocessors, content-addressable memory, and the like)configured to make wire speed decisions on how to handle incoming(ingress) and outgoing (egress) network packets. In accordance with someembodiments some aspects of the present disclosure can be performedwholly within the data plane.

Further Examples

In accordance with the present disclosure, a method in a network devicecomprises receiving a packet from an access point (AP) coupled to thenetwork device, the received packet containing an inner packet sent tothe AP from a host associated with the AP; identifying the associatedhost from the inner packet contained in the received packet; storinginto a forwarding database of the network device an entry thatrepresents a mapping between the identified associated host and the AP;advertising, to a plurality of network devices, a next hop message thatrepresents a mapping between the identified associated host and thenetwork device; and advertising, to the plurality of network devices, aparticipation message that indicates participation by the network devicein flood lists that target a communication domain to which the APbelongs.

In some embodiments, the AP coupled to the network device and the APscoupled to the plurality of network devices define a network segment,wherein the network device receives packets from the network segment.

In some embodiments, the next hop message informs each of the pluralityof network devices that the network device is a next hop for packetsdestined for the identified associated host.

In some embodiments, the participation message informs each networkdevice in the plurality of network devices to include the network devicein a flood list of said each network device in connection withprocessing a broadcast, unicast unknown, or multicast (BUM) packet.

In some embodiments, the method further comprises receiving a next hopmessage advertised by a second network device among the plurality ofnetwork devices, the received next hop message identifying a remotehost, wherein the second network device is a next hop to reach theremote host; and storing an entry in the forwarding database of thenetwork device that represents a mapping between the remote host and thesecond network device.

In some embodiments, the method further comprises the network deviceforwarding the received packet, including: identifying a second networkdevice among the plurality of network devices as a next hop networkdevice based on next hop messages previously advertised by the pluralityof network devices; and forwarding the received packet to the identifiednext hop network device.

In accordance with the present disclosure, a network device comprisesone or more computer processors; and a computer-readable storage mediumthat comprises instructions for controlling the one or more computerprocessors to: receive a first packet from an access point (AP), thefirst packet containing an inner packet that was sent to the AP from ahost associated with the AP; store a mapping between the host and theAP; receive a second packet from a second network device among aplurality of network devices, wherein the second packet contains datathat is destined for the host associated with the AP; and forwarding thereceived second packet to a next hop, wherein the next hop is identifiedusing the stored mapping between the host and the AP.

In some embodiments, the second packet is sent from a host associated toa second AP coupled to the second network device, wherein the AP coupledto the network device and the second AP define a network segment.

In some embodiments, the computer-readable storage medium furthercomprises instructions for controlling the one or more computerprocessors to advertise a next hop message to the plurality of networkdevices that represents a mapping between the host and the networkdevice, in response to receiving the first packet. In some embodiments,the next hop message informs the plurality of network devices that thenetwork device is a next hop for packets destined for the host.

In some embodiments, the computer-readable storage medium furthercomprises instructions for controlling the one or more computerprocessors to: receive a next hop message from one of the plurality ofnetwork devices, the received next hop message including a mappingbetween a remote host and said one of the plurality of network devices,wherein said one of the plurality network devices is a next hop to reachthe remote host; and store an entry in the forwarding database of thenetwork device that represents the mapping between the remote host andsaid one of the plurality of network devices.

In some embodiments, the computer-readable storage medium furthercomprises instructions for controlling the one or more computerprocessors to: identify one of the plurality of network devices as anext hop based on next hop messages previously advertised by the networkdevices in the plurality of network devices and received by the networkdevice; and forward an egress packet generated from the received packetto the identified next hop.

In some embodiments, the computer-readable storage medium furthercomprises instructions for controlling the one or more computerprocessors to advertise a participation message to the plurality ofnetwork devices, in response to receiving the first packet, theparticipation message indicating the network device's participation inflood lists that target a communication domain to which the AP belongs.In some embodiments, the participation message informs each networkdevice in the plurality of network devices to include the network devicein a flood list of said each network device in connection withprocessing a broadcast, unicast unknown, or multicast (BUM) packet. Insome embodiments, the network device advertises the participationmessage in response to the first packet being a packet received from thecommunication domain for the first time.

In accordance with the present disclosure, a network device comprisesone or more computer processors; and a computer-readable storage mediumcomprising instructions for controlling the one or more computerprocessors to: receive a packet from an access point (AP), the packetcontaining an inner packet sent to the AP from a host associated withthe AP; and advertise, in response to receiving the packet from the AP,a participation message to a plurality of network devices that indicatesparticipation by the network device in flood lists that target acommunication domain to which the AP belongs.

In some embodiments, the AP coupled to the network device and the APscoupled to the plurality of network devices define a network segment.

In some embodiments, the computer-readable storage medium furthercomprises instructions for controlling the one or more computerprocessors to store the AP in a flood list of the network deviceassociated with the communication domain to which the AP belongs.

In some embodiments, the participation message informs each networkdevice in the plurality of network devices to include the network devicein said each network device's respective flood lists for processing abroadcast, unicast unknown, or multicast (BUM) packet.

In some embodiments, the network device advertises the participationmessage in response to the received packet being a packet received fromthe communication domain for the first time.

The above description illustrates various embodiments of the presentdisclosure along with examples of how aspects of the present disclosuremay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present disclosure as defined by thefollowing claims. Based on the above disclosure and the followingclaims, other arrangements, embodiments, implementations and equivalentsmay be employed without departing from the scope of the disclosure asdefined by the claims.

1. A method in a network device, the method comprising: receiving apacket from an access point (AP) coupled to the network device, thereceived packet containing an inner packet sent to the AP from a hostassociated with the AP; identifying the associated host from the innerpacket contained in the received packet; storing into a forwardingdatabase of the network device an entry that represents a mappingbetween the identified associated host and the AP; advertising, to aplurality of network devices, a next hop message that represents amapping between the identified associated host and the network device;and advertising, to the plurality of network devices, a participationmessage that indicates participation by the network device in floodlists that target a communication domain to which the AP belongs.
 2. Themethod of claim 1, wherein the AP coupled to the network device and APscoupled to the plurality of network devices define a network segment,wherein the network device receives packets from the network segment. 3.The method of claim 1, wherein the next hop message informs each of theplurality of network devices that the network device is a next hop forpackets destined for the identified associated host.
 4. The method ofclaim 1, wherein the participation message informs each network devicein the plurality of network devices to include the network device in aflood list of said each network device in connection with processing abroadcast, unicast unknown, or multicast (BUM) packet.
 5. The method ofclaim 1, further comprising the network device: receiving a next hopmessage advertised by a second network device among the plurality ofnetwork devices, the received next hop message identifying a remotehost, wherein the second network device is a next hop to reach theremote host; and storing an entry in the forwarding database of thenetwork device that represents a mapping between the remote host and thesecond network device.
 6. The method of claim 1, further comprising thenetwork device forwarding the received packet, including: identifying asecond network device among the plurality of network devices as a nexthop network device based on next hop messages previously advertised bythe plurality of network devices; and forwarding the received packet tothe identified next hop network device.
 7. A network device comprising:one or more computer processors; and a computer-readable storage mediumcomprising instructions for controlling the one or more computerprocessors to: receive a first packet from an access point (AP), thefirst packet containing an inner packet that was sent to the AP from ahost associated with the AP; store a mapping between the host and theAP; receive a second packet from a second network device among aplurality of network devices, wherein the second packet contains datathat is destined for the host associated with the AP; and forwarding thereceived second packet to a next hop, wherein the next hop is identifiedusing the stored mapping between the host and the AP.
 8. The networkdevice of claim 7, wherein the second packet is sent from a hostassociated to a second AP coupled to the second network device, whereinthe AP coupled to the network device and the second AP define a networksegment.
 9. The network device of claim 7, wherein the computer-readablestorage medium further comprises instructions for controlling the one ormore computer processors to advertise a next hop message to theplurality of network devices that represents a mapping between the hostand the network device, in response to receiving the first packet. 10.The network device of claim 9, wherein the next hop message informs theplurality of network devices that the network device is a next hop forpackets destined for the host.
 11. The network device of claim 7,wherein the computer-readable storage medium further comprisesinstructions for controlling the one or more computer processors to:receive a next hop message from one of the plurality of network devices,the received next hop message including a mapping between a remote hostand said one of the plurality of network devices, wherein said one ofthe plurality network devices is a next hop to reach the remote host;and store an entry in the forwarding database of the network device thatrepresents the mapping between the remote host and said one of theplurality of network devices.
 12. The network device of claim 7, whereinthe computer-readable storage medium further comprises instructions forcontrolling the one or more computer processors to: identify one of theplurality of network devices as a next hop based on next hop messagespreviously advertised by the network devices in the plurality of networkdevices and received by the network device; and forward an egress packetgenerated from the received packet to the identified next hop.
 13. Thenetwork device of claim 7, wherein the computer-readable storage mediumfurther comprises instructions for controlling the one or more computerprocessors to advertise a participation message to the plurality ofnetwork devices, in response to receiving the first packet, theparticipation message indicating the network device's participation inflood lists that target a communication domain to which the AP belongs.14. The network device of claim 13, wherein the participation messageinforms each network device in the plurality of network devices toinclude the network device in a flood list of said each network devicein connection with processing a broadcast, unicast unknown, or multicast(BUM) packet.
 15. The network device of claim 13, wherein the networkdevice advertises the participation message in response to the firstpacket being a packet received from the communication domain for thefirst time.
 16. A network device comprising: one or more computerprocessors; and a computer-readable storage medium comprisinginstructions for controlling the one or more computer processors to:receive a packet from an access point (AP), the packet containing aninner packet sent to the AP from a host associated with the AP; andadvertise, in response to receiving the packet from the AP, aparticipation message to a plurality of network devices that indicatesparticipation by the network device in flood lists that target acommunication domain to which the AP belongs.
 17. The network device ofclaim 16, wherein the AP coupled to the network device and APs coupledto the plurality of network devices define a network segment.
 18. Thenetwork device of claim 16, wherein the computer-readable storage mediumfurther comprises instructions for controlling the one or more computerprocessors to store the AP in a flood list of the network deviceassociated with the communication domain to which the AP belongs. 19.The network device of claim 16, wherein the participation messageinforms each network device in the plurality of network devices toinclude the network device in said each network device's respectiveflood lists for processing a broadcast, unicast unknown, or multicast(BUM) packet.
 20. The network device of claim 16, wherein the networkdevice advertises the participation message in response to the receivedpacket being a packet received from the communication domain for thefirst time.